Carburetor



Dec. 15, 1925 R. T. STEWART GARBURETOR o i l Filed May 29, 1916 2, Sheets-Sheet 1 e zdffziewarzfi 75% WW "4%;

Dec. 15, 1925.

R. T. STEWART CARBURETOR 2 Sheets-Sheet 2 Original ed May 29, 1916 v JMGIZZ OIT State of 35 extent Patented 15. 1925.

UNITED STATES REID T. STEWART, PITTSBURGH, PENNSYLVANIA.

GARBUBETOB.

Original application ruled lay 89, 1916, Serial No. 100,436. Divided and this application filed August 88,

on. Serial m. 319,866.

To all whom it may comem:

Be it known that I, Ram T. STEWART, a citizen of the United States, residing at Pittsbur h, in the county of Allegheny and ennsylvania, have invented a new and useful Improvement in Carburetors, of which the following is a full, clear, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

My invention has relation to fuel supply systems for internal combustion engines, and more particularly to a system of this character which is designed for use when the main 16 source of fuel supply is either permanently or temporarily located at a lower level than the carburetor, and in which the suction of the engine is utilized to cause a flow of the fuel from'the main source of supply to the Z carburetor.

One object of my invention is to provide a carburetor which shall be simple in construction andioperation and which shall be especially adapted for use in such an improved system of vacuum fuel feed.

, conditions.

Another object is to provide a vacuum fuel feed system, in which the vacuum is continuous in its action and in which the vacuum ran e may be made less to any desired an that in the engine manifold.

A further object of the invention is to rovid'emeans'whereby,the fuel feed may g operated practically continuously with a small degree of vacuum, with open throttle,

/and therefore, with high volumetric engine efliciency, thereby giving the maximum power when power is most demanded, while at the same time, suflicient vacuum may be had with a artially closed throttle for lifting the fue to the top of a supplemental supply tank.

A further object of my invention 15 to provide a novel and efiicientform and arrangement of inlet valve,part1cularly adapted for use in connection with an improved fuel feed of the character above outlined so as to provide a better admixture of the fuel and an.

A still further object is-to provide appara- 66 tus of this kind, in which the parts are few andsimple in character and can be readily assembled and which are readily accessible for renewal or repairs.

My invention will be more readily understood by reference to said drawings in which:

Figure l is a sectional elevation illustrat- 111% one form of my invention; and

igure 2 is a similar view illustrating another form of my invention.

In Figure 1, the numeral 1 designates a supplementaltank which is supplied with liquid fuel by means of an unrestricted passage 2, connecting its upper portion with a main fuel supply tank 3. A partial vacuum is maintained in the supplemental tank by means of a restricted passage 4, which connects its upper portion with the upper portion of the float chamber 5, and which acts also as a fuel passage, as will be described. The float chamber 5, communicates by means of a passage 6 with the carbureting chamber 7 wherein partial vacuum exists. In the form shown in this figure, I have shown the pipe or tube forming the passage 4 as extending upwardly through the supplemental tank, which isshown as supported directly upon the float chamber. 8 designates another fuel feed passage leading from the bottom of the supplemental tank into the upper portion of the float chamber. The passages 4 and 8 are controlled, respectively by valves 10 and 12, whose stems 11 and 13 rest upon the top of a float 14, preferably at diametrically opposite points and equidistant from the axis through the center of buoyancy. The weight of the valve 10 and its stem 11 is made greater than that of the valve 12 and its stem 13, (or the left side of the float may be overweighted in any other suitable manner) thereby giving a tendency to the float to list toward the side which carries the heavier load and in order that the valve 10' may always open before the valve 12. The float is preferably mounted on a vertical tapered pin 15, the float having a central openlng engaging said pin in a manner to permit of t e free vertical movement of the float, combined with a limited oscillating or tipping movement. The extent of the actual tipping movement of the float, due to the excess weight on the side of the valve 10, is preferably limited by the amount of taper to be 'ven to. the pin 15, or it may be to the we] of the opening 16. This taper is made sufilcient to cause the valve 12 to open the instant that sufficient fuel ceases to enter past the valve 10.

The passage 4, which connects the top of the supplemental tank 1 with the upper portion of the float chamber, acts as a main fuel feed passage, as a suction or vacuum passage, and also as an air and fuel vapor vent. This passage, controlled in the manner described, functions to maintain a store of fuel in the supplemental tank up to the level shown in Figure 1, whenever the vacuum produced by the engine is suflicient to lift the fuel to the top of the supplemental tank. Any condition which causes an interruption of fuel flow to the float chamber 5, by way of the main fuel passage 4, will automatically put into action the supplemental fuel passage 8, whereby the fuel will be drawn from the supply stored in the supplemental tank until such time as the passage 4 resumes its normal operation.

The air inlet 18 of the carbureting chamher 7 is controlled by a valve 17. This valve is held to its seat 19 primarily by means of the spring 20, and secondarily by means of a piston 21, attached thereto and slidably mounted within the cylinder 22, whichis supported within or adjacent to the air inlet 18. The upper end of the cylinder 22 is closed, and the space within communicates by means of a passage 23 with the carburetor outlet 24: on the engine side of the throttle valve 25. When the throttle valve is wide open, as indicated in the dotted posilow valve stem 27, and is distributed to the periphery of the valve 17 by means of the passage or passages 28, formed within the air valve itself and leading to the outlet 26. This outlet 26 preferably consists of a narrow slot extending around the periphery of the valve, the latter being formed in two sections, as shown, to provide for this slot, which is located at the point of contact of the valve with said seat. I prefer to incline the distributing passage 28 and the fuel outlet opening 26 downwardly or in the direction of flow of the air for the purpose of causing the fuel to issue more or less in the direction taken by the air while passing through the throat of the air passage. By the combined action of the air valve 17, the fuel outlet 26, the vacuum piston 21, the passage 23, and the throttle 25, I am enabled to produce a perfect admixture of the fuel with the air' when such condition is desired, viz, when operating under partially closed throttle, especially when using liquid fuels which vaporize with difficulty.

The lower end of the hollow valve stem 27 has secured thereto a piston 29, working in the liquid dash pot 29 which may be supplied from the float chamber by means of openings 29 in the piston. The purpose of this dash pot is to prevent any tendency of the valve 17 to vibrate or flutter. The piston 29 has a depending hollow hub or sleeve which telescopes over a metering pin 30, and which terminates in the annular seat 32. This pin is of gradually reduced diameter tion 25 the vacuum in cylinder 22 is sub-toward its lower end, and said pin is of sufstantially equal to that in the carbureting chamber 7, and for this condition the pressure of valve 17 "against its seat is due to the action of the spring 20 alone. hen, however, the throttle valve is partially closed, as indicated in full lines in said drawin the degree of vacuum is greater in the cy inder 22 than it is in the carbureting chamber 7. This causes, the piston 21 to exert an upward pull on the air valve 17. This upward pull, which is substantially zero with a wide open throttle, may be increased to any desired extent for partially closed throttle, by suitably enlarging the diameter of the piston 21, with respect to the air valve 17 This construction and arrangement makes it possible to operate a vacuum fuel feed system during positions of partially or substantially closed throttle, when, in the ordinary carburetor construction, there would be a relatively low or small degree of vacuum in the carbureting chamber.

fuel is preferably drawn up through the holficient weight to seat firmly upon an adjusting screw 35. The weighted lower end 31 has therein a cone shaped cavity 33, which engages the conical point 34 of the adjusting screw 35. This construction provides in a simple manner for the longitudinal adjustment of the metering pin and also a perfect means of lateral self-adjustment of the pin to its surrounding seat 32. The construction and arrangement also permits of the parts being'readily assembled and easily accessible for any desired purpose. The lower section 29 of the dash pot 29 is made removable for this purpose.

In Figure 2, I have shown still another embodiment of my invention, generally similar to that shown in Figure 1, but involving a number of modifieaions. Parts of this figure which correspond to similar parts in Figure 1 are given the same reference numerals with the letter K afiixed. It will be noted that in Figure 2, the valve 17 is reversed with respect to the valve 17 of Figure 1, and is arranged to seat downwardly by gravityin-v stead of being within the stem of the valve,

as in Figure 1, is formed by a separate pas-' sage 56 in the wall of the carburetor, and communicates with an annular passage 57 below the seat for the valve 17", and communicates with the seating surface by an annular discharge slot 58. The fuel is thus discharged at a similar point to that of Figure 1. The metering pin 30 is carried by the dash pot piston 29 and adjustment thereof is obtained by providing. the stem 27 of the valve with a slotted head 59. The lower end of the valve stem has a threaded connection at 61 with the piston 29-. The correct adjustment is secured by means of a pawl or detent. 62, engaging'the toothed- Wheel 63 on the lower end of the valve stem. By removing the cap 60, the stem 27 can be turned by means of a screw driver, thus raising or lowering the piston and correspondingly adjusting the metering pin.

In this figure I have also shown a modified arrangement of the float 14, in which the centering pin 15 of Figure 1 is omitted and substantiall by making the oat of downwardly tapered or frusto-conical form. The side of the float upon Whichthe valve stem 11 rests is overweighted with respect to the opposite side either by the increased weight of said stem or in any other suitable manner.

It will be readily understood that the double valve arrangement herein shown and described effectively providesfor the prop-- er supply of fuel to the float chamber under all conditions. So long as the vacuum action produced by the engine is suflicient to maintain the supplemental tank filled to about the level shown, the supply to the float chamber is past the main valve. When,

the same result is obtained cally provides,when requirethfree cominunication between the upper portions of the supplemental tank and the float chamber for the purposes of venting and of transfer of suction.

As it i.\ obvious that my invention is capaiie of various modifications, I do not limit my invention to the specific structures herein shown and described.

This present application is a division of my copending application filed May 29th, 1916, Serial No. 100,436, which was in part a continuation of my earlier application, Serial No. 72.384, filed January 17th. 1916.

I claim.

In a carburetor, the combination of a carbureting chamber, a fuel inlet to said chamber, an air inlet to said chamber, an element movable to difi'erent positions under different conditions of operation, a hollow stem movable by said element and adapted to supply fuel to said fuel inlet, a restricting orifice associated with said hollow stem, a tapered metering pin cooperating with said restricting orifice, and an adjustable pointed supporting member engaging in a recess in said metering pin for permitting lateral movement of said pin on said supporting member.

In witness whereof I hereunto subscribe my name this 21st day of August 1919.

REID T. STEVART. 

